By the time the rain stops, Harvey will have dumped about 1 million gallons of water for every man, woman and child in southeastern Texas.

This, say scientists, is- a soggy, record-breaking glimpse of the wet and wild future that global warming could bring.

Some have even gone as far as to say such extreme storms are 'the new normal'.

While researchers are quick to say that climate change didn't cause Harvey, they do note that warmer air and water mean wetter and possibly more intense hurricanes in the future.

'This is the kind of thing we are going to get more of,' said Princeton University climate scientist Michael Oppenheimer. 'This storm should serve as warning.'

Tropical Storm Harvey, say scientists, is- a soggy, record-breaking glimpse of the future. Pictured are volunteer rescue boats making their way into a flooded subdivision to rescue stranded residents as floodwaters from Harvey rise

There's a scientifically accepted method for determining if some wild weather event has the fingerprints of man-made climate change, and it involves intricate calculations.

Those could take weeks or months to complete, and then even longer to pass peer review.

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In general, though, climate scientists agree that future storms will dump much more rain than the same size storms did in the past.

That's because warmer air holds more water.

With every degree Fahrenheit, the atmosphere can hold and then dump an additional 4 percent of water (7 percent for every degree Celsius), several scientists say.

John and Cathy Cservek hold their dogs Lacy and Iggy while being rescued from their home as floodwaters from Harvey rises. Scientists say warmer air and water mean wetter and possibly more intense hurricanes in the future

David Helvarg, executive director of Blue Frontier, an ocean conservation organization told Democracy Now that storms like Harvey are the new normal.

'The reality is, when you have two 10,000-year rain events in two years, this is the new normal.

'This is the new reality. And the challenge is how we address it. How rapidly we’re going to transition from fossil fuels to clean energy.'

Global warming also means warmer seas, and warm water is what fuels hurricanes.

When Harvey moved toward Texas, water in the Gulf of Mexico was nearly 2 degrees (1 degree Celsius) warmer than normal, said Weather Underground meteorology director Jeff Masters.

Hurricanes need at least 79 degrees F (26 C) as fuel, and water at least that warm ran more than 300 feet (100 meters) deep in the Gulf, according to University of Miami hurricane researcher Brian McNoldy.

Several studies show that the top 1 percent of the strongest downpours are already happening much more frequently.

Also, calculations done Monday by MIT meteorology professor Kerry Emanuel show that the drenching received by Rockport, Texas, used to be maybe a once-in-1,800-years event for that city, but with warmer air holding more water and changes in storm steering currents since 2010, it is now a once-every-300-years event.

WHY HURRICANE HARVEY IS WORSE THAN OTHERS

Hurricane Harvey's biggest effect is through its intense and prolonged rainfall. A low pressure system to the north is keeping Harvey over southern Texas, resulting in greater rainfall totals.

We know that climate change is enhancing extreme rainfall . As the atmosphere is getting warmer, it can hold more moisture (roughly 7 per cent for every 1℃ rise in temperature).

This means that when we get the right circumstances for very extreme rainfall to occur, climate change is likely to make these events even worse than they would have been otherwise.

Without a full analysis it is hard to put exact numbers on this effect, but on a basic level, wetter skies mean more intense rain.

But there are also other factors that are making this story worse than others in terms of its impact.

Houston is the second-fastest growing city in the US, and the fourth most populous overall.

As the region's population grows, more and more of southern Texas is being paved with impermeable surfaces .

This means that when there is extreme rainfall, the water takes longer to drain away, prolonging and intensifying the floods.

There is a trend towards more tropical storms and hurricanes in the North Atlantic. It is likely that climate change has contributed to this trend, although there is low statistical confidence associated with this statement

Hurricane Harvey's biggest effect is through its intense and prolonged rainfall. A low pressure system to the north is keeping Harvey over southern Texas, resulting in greater rainfall totals

There's a lot of debate among climate scientists over what role, if any, global warming may have played in causing Harvey to stall over Texas, which was a huge factor in the catastrophic flooding.

If the hurricane had moved on like a normal storm, it wouldn't have dumped as much rain in any one spot.

Harvey stalled because it is sandwiched between two high-pressure fronts that push it in opposite directions, and those fronts are stuck.

Oppenheimer and some others theorize that there's a connection between melting sea ice in the Arctic and changes in the jet stream and the weather patterns that make these 'blocking fronts' more common.

Others, like Masters, contend it's too early to say.

University of Washington atmospheric scientist Cliff Mass said that climate change is simply not powerful enough to create off-the-chart events like Harvey's rainfall.

'You really can't pin global warming on something this extreme.

'It has to be natural variability,' Mass said. 'It may juice it up slightly but not create this phenomenal anomaly.'

'We're breaking one record after another with this thing,' Mass said.

A rescue boat enters a flooded subdivision as floodwaters from Tropical Storm Harvey rise. There's a lot of debate among climate scientists over what role, if any, global warming may have played in causing Harvey to stall over Texas